Long Distance Migration
Some of the common summer residents of North America are not content with a trip to northern tropical areas of the West Indies and Central America, but push on across the Equator and finally come to rest for the winter in Patagonia or the pampas of Argentina. Species such as nighthawks, some barn swallows, cliff swallows, and a few thrushes may occupy the same general winter quarters in Brazil, but other nighthawks and barn swallows go farther south. Of all North American landbirds these species probably travel the farthest; they are found north in summer to the Yukon Territory and Alaska, and south in winter to Argentina, 7,000 miles away. Such seasonal flights are exceeded in length, however, by the remarkable journeys of several species of shorebirds including white-rumped and Baird's sandpipers, greater yellowlegs, turnstones, red knots, and sanderlings. In this group, 19 species breed north of the Arctic Circle and winter in South America; six of these go as far south as Patagonia, a distance of over 8,000 miles.
The Arctic tern is the champion "globe trotter" and long-distance flier ([Fig. 11.]). Its name "Arctic" is well earned, as its breeding range is circumpolar and it nests as far north as the land extends in North America. The first nest found in this region was only 7½° (518 miles) from the North Pole and contained a downy chick surrounded by a wall of newly fallen snow scooped out by the parent. In North America the Arctic tern breeds south in the interior to Great Slave Lake, and on the Atlantic coast to Massachusetts. After the young are grown, the Arctic terns disappear from their North American breeding grounds and turn up a few months later in the Antarctic region, 11,000 miles away. For a long time the route followed by these hardy fliers was a complete mystery; although a few scattered individuals have been noted south as far as Long Island in the United States, the species is otherwise practically unknown along the Atlantic coasts of North America and northern South America. It is, however, known as a migrant on the west coast of Europe and Africa. By means of numbered bands, a picture disclosed what is apparently not only the longest, but also one of the most remarkable migratory journeys (Austin 1928).
Figure 11. Distribution and migration of arctic terns. The route indicated for this bird is unique, because no other species is known to breed abundantly in North America and to cross the Atlantic Ocean to and from the Old World. The extreme summer and winter homes are 11,000 miles apart.
Few other animals in the world enjoy as many hours of daylight as the Arctic tern. For these birds, the sun never sets during the nesting season in the northern part of the range, and during their winter sojourn to the south, daylight is continuous as well. In other months of the year considerably more daylight than darkness is encountered.